1. Field of the Invention
The present invention relates to a single phase line start permanent magnet synchronous motor, and particularly, to a single phase line start permanent magnet synchronous motor by which a driving efficiency can be improved, a structure can be compact, and a manufacturing cost can be reduced.
2. Description of the Background Art
Generally, a brushless direct current motor is used as a fan motor for a refrigerator, a microwave oven, a humidifier, and a small electric fan because the brushless direct current motor has a simple structure and costs a little.
The brushless direct current motor has relatively higher efficiency than that of an alternating current motor, a speed of the motor can be changed by controlling an applied electric power, and has high reliability and long life span.
FIG. 1 is a partially cross-sectional view showing a conventional brushless direct current motor in longitudinal direction, FIG. 2 is a rear elevation view showing the conventional brushless direct current motor, and FIG. 3 is a front view showing a stator core of the conventional brushless direct current motor.
As shown therein, the brushless direct current motor comprises: a rotor 111; a stator 121 for receiving the rotor 111 with a certain air gap therebetween; a PCB (Printed Circuit Board) 136 for forming a drive circuit; and a PCB cover 137 coupled to one side of the stator 121 for receiving the PCB 136.
The rotor 111 is formed to have circular cross section using a permanent magnet, and a rotary shaft 112 is coupled to the shaft of the rotor 111 as a single body.
In addition, a pair of bearing housings 113 including bearings 115 for supporting the rotary shaft 112 are coupled to both sides of the rotor 111 along with a direction of shaft line of the rotary shaft 112.
Also, as shown in FIGS. 1 and 3, the stator 121 comprises: a first stator core 122 including a first pole-shoe 123 and a second pole-shoe 125, which are facing each other with a predetermined air gap, formed as a single body; a second stator core 132 coupled to one side of the first stator core 122 as a single body; and a bobbin 133, on which a coil 135 is wound a plurality of times, coupled in an inner space 138 formed by coupling the first stator core 122 and the second stator core 132 as penetrating the inner space 138.
In addition, the first stator core 122 and the second stator core 132 are fixed and coupled as a single body with each other by insulatingly stacking a plurality of steel sheets. And a first detent groove 127 and a second detent groove 129, which are apart from an outer diameter surface in a radial direction, and extended as a predetermined width via a circumferential direction for starting the rotor 111, are formed on the first stator core 122 respectively.
On the other hand, a PCB cover 137 for receiving the PCB 136 is disposed on one side of the bobbin 133 via the rotary shaft line direction of the rotor 111, and a sensor receiving part 139 is formed on the PCB cover 137 so as to receive and support a position sensor (not shown) which is disposed between the bobbin 133 and the rotor 111 for sensing a rotary position of the rotor 111 (see FIG. 1).
In the above brushless direct current motor, the first detent groove 127 and the second detent groove 129 are formed on the first pole-shoe 123 and on the second pole-shoe 125 so that the rotor 111 is not disposed on a position where an electric torque is zero for starting the rotor 111. However, the air gap is enlarged by forming the detent grooves, and then an effective magnetic flux is reduced and an efficiency of the motor is lowered.
Also, an additional direct current supplying device (not shown) which has a large volume and costs high should be disposed in order to drive the motor making the utility alternating current as an input power, and a drive circuit for driving the rotor 111 and the position sensor (not shown) for sensing the position of the rotor 111 are should be included, a volume and price of the motor are increased.
Therefore, an object of the present invention is to provide a single phase line start permanent magnet synchronous motor by which a driving efficiency of the motor can be improved, a structure of the motor is compact, and a manufacturing expense can be reduced.
To achieve the object of the present invention, as embodied and broadly described herein, there is provided a single phase line start permanent magnet synchronous motor comprising: a rotary shaft; a rotor core coupled on outer circumferential surface of the rotary core so as to be rotatable; a plurality of permanent magnets fixedly inserted into the rotor core in rotary shaft direction and disposed so as to be apart from each other in circumferential direction; a rotor including a secondary conductor fixedly inserted between protruded parts of the rotor core in rotating shaft line direction; a stator located on an outer circumferential surface of the rotor with a predetermined air gap therebetween; bearings for supporting both end parts of the rotary shaft in shaft line direction of the rotary shaft so as to support the rotary shaft; a first housing, through which the rotary shaft is penetrated, coupled to the outer circumferential surface of the stator for receiving bearing on one side among those bearings; and a second housing, through which the rotary shaft penetrates, coupled on one side of the first housing for receiving the bearing on the other side among the bearings.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.